1. Field of the Invention
The invention relates to a light source module, and more particularly to a planar light source and a method of manufacturing such planar light source.
2. Related Art
At present, in an edge-lighting planar light source module having light-emitting diodes (LEDs) serving as a light source, a plurality of LEDs is mounted on a substrate body. FIGS. 1a and 1b are a side view and a top view, respectively, showing an embodiment adopting a light guide plate. Referring to FIGS. 1a and 1b, the edge-lighting light source module includes a light guide plate 2 and a plurality of LEDs 10. The light guide plate is typically formed by acrylic by way of injection molding. A diffusion plate 22 and a reflective plate 24 are disposed above and below the light guide plate 2, respectively. The substrate body is a light bar 12. The LED 10 is disposed on one side of the light bar 12. Then, a light-emitting surface of the light bar 12 is aligned with a light input surface 20 of the light guide plate 2. The light, after being reflected by the reflector 24, scatters from the diffuser 22 and is converted into the uniform surface light source.
FIGS. 2a and 2b are a front view and a top view, respectively, showing another conventional light source module, in which a planar light guide plate 4 is adopted, and two light bars 12 and LEDs 10 are disposed on two sides of the planar light guide plate 4.
The light bar is usually a strip-like substrate body, on which a positive pole electroconductive track and a negative pole electroconductive track are formed or disposed. When the light bar is being manufactured, packaged LEDs are sequentially disposed on the strip-like substrate body, and the positive and negative pole ends of each packaged LED are electrically connected to the positive and negative pole electroconductive tracks of the strip-like substrate body, respectively.
In the LED package, the LED chip is usually bonded to the lead frame containing the housing, and the electrodes are led out of the lead frame by way of metal wire bonding, and then the organic resin, such as silicone gel or epoxy resin, containing fluorescent powders are coated to form the package body.
In order to make the light source module obtain the uniform brightness, a material having the refractive index different from that of the acrylic plate is usually printed on the surface of the light guide plate, or refracting surfaces with different angles are directly formed on the surface of the light guide plate. FIGS. 3a to 5b are front views and top views, respectively, showing three conventional edge-lighting light source modules. In FIGS. 3a and 3b, an ink layer 30 composed of the transparent resin and containing light scattering particles is formed on the second surface 18 of the light guide plate 2. In FIGS. 4a and 4b, a plurality of rough blocks 40 is formed on the second surface 18 of the light guide plate 2 so that the second surface 18 becomes the concave-convex surface. In FIGS. 5a and 5b, a plurality of dents 50 is formed on the second surface 18 of the light guide plate 2 so that the second surface 18 becomes the sawtooth surface. The three examples make the light uniform by increasing the reflecting or scattering area. However, the efficiency of the existing art is directly proportional to the thickness of the light input surface 20 of the light guide plate and the machining smoothness of the mirror of the light input surface 20. Under the considerations of the cost, weight and thickness, the efficiency often has to be sacrificed to obtain the balance among various aspects. In addition, the difference between the refractive indexes of the LED package body and the air causes the total reflection, and the separation of the light source from the light guide plate loses the light to decrease the illumination.
In addition, due to the thickness restriction of the light guide plate and the convenience of manufacturing the light bar, the current edge-lighting light source module usually adopts the surface mounted device (SMD) LEDs with the lower power. This kind of LED usually has the poor light-emitting efficiency and heat dissipating effect due to the external shape and the structure restriction, and the high current driving cannot be used. So, many LEDs are required, and the overall efficiency of the light source module is poor and the complicated manufacturing processes are caused. Although the edge-lighting planar light source module has the advantages of the thinned structure, and the soft and uniform high quality light source, the cost is too high. In addition to the application to the backlight module of the liquid crystal display, the edge-lighting planar light source module is not popular in the ordinary illumination market.
Therefore, the invention provides a LED light bar and related planar light source and a method of manufacturing the same to overcome the problems. The embodied architecture and implementation will be described in the following.